(a) Technical Field
The present invention relates to a method for manufacturing valve train parts using metal powder injection molding, more particularly, to a method for manufacturing valve train parts using metal powder injection molding having improved physical properties by replacing the conventional investment casting method with metal powder injection molding, which has greater dimensional accuracy thereby reducing the cost, and by controlling the powder composition.
(b) Background Art
An internal-combustion engine is an apparatus generating powder by combusting air and a fuel, which are suctioned from the exterior, in a combustion chamber, and the apparatus has an intake valve for suctioning the air and the fuel into the combustion chamber and an exhaust valve for releasing detonated gas combusted in the combustion chamber. These intake and exhaust valves open and close by a camshaft, which rotates by interlocking to the rotation of a crankshaft. Additionally, a series of parts for operating the intake and exhaust valves, such as a drive cam, a camshaft, a tappet, a rocker arm and a rocker arm link, is called a valve train.
Moreover, the automobile industries are developing various environmentally friendly vehicles by aiming to reduce carbon dioxide emissions to 50 g/km, which is 35˜50% of the current level, until 2020, and the industries are concentrating on technical development to satisfy fuel efficiency of 23.2 km/l (54.5 mpg), US Corporate Average Fuel Economy regulations in 2025.
Recently, a Continuous Variable Valve Lifter (CVVL), which maximizes fuel efficiency and engine performance by optimizing the amount of air intake by controlling the height of the intake valve according to engine rotation speed, is being applied to a vehicle engine.
FIG. 1 is an exemplary view showing a rocker arm; FIG. 2 is an exemplary view showing a rocker arm link; FIG. 3 is an exemplary view showing a combination structure of a rocker arm and a rocker arm link; and FIG. 4 is an exemplary view showing a continuous variable valve lifter, and as shown in FIGS., the rocker arm 100 and the rocker arm link 110 work as the parts of the continuous variable valve lifter 120.
Since the valve train parts such as the rocker arm 100 and the rocker arm link 110 must be used for long periods of time under harsh conditions, a high durability and accuracy such as strength, abrasion resistance, and impact resistance are needed.
Previously, the investment casting method, which has relatively higher dimensional accuracy compared with common casting methods, was used to manufacture the valve train parts, but there is a need of many additional processes to obtain the final shapes after casting due to the sophisticated shapes of the valve train parts.
Moreover, when the valve train parts are manufactured by the investment casting method, they exhibit high mechanical strength but reduced dimensional accuracy and thus the processing cost and material loss due to the additional processes increased.
The description provided above as a related art of the present invention is just for helping understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.